The short answer: those red and blue plastic lines are PEX tubing — short for cross-linked polyethylene — and they’re one of the best advances in residential building technology in decades. Red carries hot water, blue carries cold. If your home was built in roughly the last twenty years, PEX is very likely what’s supplying your faucets; in older homes you’ll see the familiar shiny copper pipe instead.
Why builders moved away from copper
Copper was a massive improvement over the lead and clay pipe that came before it, and it served homes well since the 1920s. But it has real drawbacks:
- It’s expensive, and the price is volatile.
- It’s rigid, so it requires lots of joints and fittings — and every fitting is a potential leak.
- It takes considerable time and skill to install.
- It’s susceptible to bursting when it freezes — a real consideration in Colorado.
- It corrodes and weakens over time.
Why PEX won
- The material costs far less than copper, and so does the installation.
- It’s flexible — it snakes through framing with minimal fittings, and long seamless runs mean fewer places to leak.
- It’s far more forgiving in freezing conditions than rigid pipe.
- It’s color-coded: installed properly, you know at a glance which lines are hot and which are cold, which makes repairs and modifications simple.
Once building departments across the country accepted PEX, it took off, and it’s now the preferred supply material in most regions — including the Pikes Peak region. We use PEX in all our homes. You’ll still see copper in places (connectors and manifolds, for example), but the hot and cold runs themselves are PEX.
Don’t confuse PEX with the old gray “poly” pipe
People sometimes lump PEX in with the gray polybutylene pipe (“PB1,” “poly pipe,” or “QEST” pipe) that was the subject of a $1.1 billion class-action settlement (Cox v. Shell) — that material was famous for failing and causing major water damage, and manufacturing ceased back in 1995. PEX is a different material entirely, proven across decades of use in the field. It’s reliable, efficient, and inexpensive — and now you know why your pipes are red and blue.
Curious how the rest of a home goes together? See how we build, or walk through homes we’ve completed.
